ERA5 almanac — 8 years of real data

Costa Rica — Manuel Antonio in January

Costa Rica — Manuel Antonio in January: 27% of days see measurable rain, 84°F average high, 37% of days historically clear (n=248, ERA5 2018–2025).

Costa Rica — Manuel Antonio in January is historically a poor month for sun: only 37% of days clear across 8 years (n=248, avg high 84°F). Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Costa Rica — Manuel Antonio page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late January

Clear-sky percentage for Costa Rica — Manuel Antonio in January, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early January 1st–15th	24%	n=120	84°F
Late January 16th–end	50%	n=128	84°F
Full month average	37%	n=248	84°F

Sunshine & warmth in January

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Costa Rica — Manuel Antonio in January. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early January 1st–15th	98%	n=120
Late January 16th–end	98%	n=128
Full month average	98%	n=248

11.1 h median sunshine per day 95% of days exceed 8 h sunshine 27% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 37%. Sunshine-based “warm & sunny”: 98%. The 61-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Costa Rica — Manuel Antonio is mostly overcast in January historically: only 37% of days are clear across 8 years (n=248), avg high 84°F. The two halves differ materially (24% early, 50% late) — favour the late half of the month. Most visitors this month will see more clouds than sun.

Every month in Costa Rica — Manuel Antonio

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Costa Rica — Manuel Antonio, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January ← this page	37%	n=248	All destinations →
February	51%	n=226	All destinations →
March	34%	n=248	All destinations →
April	8%	n=240	All destinations →
May	4%	n=248	All destinations →
June	2%	n=240	All destinations →
July	5%	n=248	All destinations →
August	3%	n=248	All destinations →
September	0%	n=240	All destinations →
October	0%	n=248	All destinations →
November	4%	n=240	All destinations →
December	22%	n=248	All destinations →

Frequently asked

Does it rain in Costa Rica — Manuel Antonio in January?

Sometimes. Costa Rica — Manuel Antonio sees measurable rain on 27% of days in January historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Costa Rica — Manuel Antonio good for sun in January?

It's mixed. Costa Rica — Manuel Antonio in January is clear on 37% of days historically (avg high 84°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Costa Rica — Manuel Antonio compares in January

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Costa Rica — Manuel Antonio this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

→ Costa Rica — Manuel Antonio vs Exuma in January — Exuma is 38% clear historically
→ Costa Rica — Manuel Antonio vs Naples in January — Naples is 35% clear historically
→ Costa Rica — Manuel Antonio vs Turks & Caicos in January — Turks & Caicos is 34% clear historically

→ Costa Rica — Manuel Antonio live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in January — all destinations ranked by January clear-sky %
→ All destinations
→ Raw data (JSON) — buckets, n, source

All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.